Apparatus for indicating voltage stress



t. '4 19 0c 27 F. c. DOBLE APPARATUS FOR INDICATING VOLTAGE STRESS FiledJune 10, 1922 174 0/ famed/ans.

Patented Get. 4,1927.

rmx c; nonnn, or cannmnen, mnsshcnnsn'rrs.

Arrarmrns Eon rnnic' rrrne {voLrAen srnn ss.

The object of the present invention is to provide an instrument ordevice which may be used, with; safety to the operator, for

I tensity of such stress. for which the device is intended is that of vcarried. Such insulators are placed between testing the insulatingqualities of electrical insulation under conditionsof. high. voltagestress, and, in general, indicating the pres?- ence of voltage stressand measuring the 1n- Onejparticular use testing the insulators by whichthe. wires. of high tension power. transmission lines, are

extremely high difierences of potential, amounting to many thousands ofvolts, but, being made almost universally of porcelain or glass, theyare comparatively fragile and are very liable to fracture and other dameage which destroys or largely dimin'ishes their insulating qualities. Atthe same time, .the conditions surrounding high tension electrical linesmake ,'it,of the utmost importance that the-insulators vbe maintained infully effective condition; and this in turn requires that insulatorsbefore being put in -beingkilled or seriously injured'by receiv ingthrough their bodieseurrent discharges from electrical conductors athigh potential above ground, imperatively requires that the testinginstrument contain safeguards.

\ adequate to protect them from thisdanger;

The testing device which forms the subject of this invention isdesignedand adapted to be placed close to, or in contactwith any part 'of "aninsulatingunit under voltage stress, .or'directly in contact with aconductor charged with the highest voltage, while the operator is incontact with ground, and itis provided with means. for" giving to theoperator a sensible indication of the exist- .ence of voltagestress atthe point at which it is so] placed, I with adequate insulationefiectively preventing appreciable current flow through the instrumentto the operator, and, preferably, with means for quantita tivelymeasuring the. value of the voltage stress indicated. Fora completedescription a of; the instrument and statement of the new.

step in the artin which the'invention consists, reterence is direc ed 9e foll w ng- 'Lpplicafipn flied .Time 10,'

, insulators;

1922. semi no. 567,288.

specification and appended claims, in connectioli with the drawingsfurnished here with.-

In said drawings,

' Figure 1' is a perspective 'view showing thepreferred embodiment ofthe invention ap-i plied to the use Figure 2 is a central section on alarger of testing so-called 'pin' type j scale of that part of thetesting device which contains. the lnd-icating means.

Figure 3-is a diagram of one of the many possible arrangements of 1 theelectrical equipment forming part of such indicating means.

Figure i is a fragmentary view showing a modification-I J 'Describing indetail the specific d'evice. thus illustrated, a' represents'the,indicating part; of the instrument, which may, for convenience, becalled an indicator or detector,- 6 represents an insulating holder,which is also pa'rtot a sound-conducting conduit, 9 represents aflexible sound-conducting tube preferably of insulating material,arranged as acontinuation of such conduit-,- and (1 represents terminalear-pieces at the ends of adapted to be placed against the ears of thebranches 0, '0" ofthe flexible tube, which are operator, and there held;if desired, by'a head band e, ofany suitable character.

The said indicating part or detector a -v comprises a terminal conductorg, a con.- denser h, a telephonic receiver is, and "a conductor-Zbetween thecondenser and receiver on the one hand,- andthe'terminalconductor g on the other hand, from which it is separated byanadjustable' gap. These parts are held in proper relation to eachother, en-

&

cased, and insulatedfrom surrounding objects and media (except as to theterminal 'point of the conductor-g) by suitably rigid andosuitablynon-conducting material, such as molded-and; vulcanized hard rubbercomand to be adjusted from-a minimum ofzero, when the conductors are incontact, to anyfdesired maximum. The opposite end of'the insulating bodym .is enlarged to form.

a chamber p inwhich are containedvthe re-- ceiver and the condenser,,and to thisbody 1s secured detachably" (here shown as by screw,

. threads) a closure q, terminating in a socket where, tests ofhightension electrical equip- Other, parts ment can feasibly be *made, ofsuch safety means coniprlse the msulating holder 6 and sound conductingconduit,

later described in detail,- by which the operator, is'enabled to use theapparatuskw'hile remaining himself at a safe distance from.

f any conductor of high potential current. We are now .concerne'd,however,. with the insulating: medium or material which encloses andencases the electrically conducftive' members of the detector. All ofsuch conducting .parts, except, preferably, the

v to which, under conditions of use, the ap smallest part which,willsufii'ce as a contact terminal (the extremity of the conductor'g')are completely enclosed by insulating mate rial of which dielectricstrength is great enough to withstand the maximum voltage a ratusis'liablesto. be subjected. It will be noted from the drawing thattheinsulating bodies m and n have substantial thickness,-

except at the terminal point,.and the thickness ofsuch insulatorsincreases away from the-exposed terminal point; and. that'the telescopicjoint between parts m and 1;], the threaded joint bet-ween'the parts m'and g encasing the telephonic receiver, and thejoint between the casingand the holder 1),

' at the socket r,-all have-substantial length. The dielectric strengthof the insulating material is great enough at any point to' sustain fromthe ,the voltage stressto which it. may be'subjected when the exposedterminal is placed in contact with aconductor carrying high tensioncurrents of the order of magnitude c-ontemplated in this specification,and the joints above referred to a rewlong enough to provide air gap--insulation of equivalent value. Thatis', the conditions prescribed byrecognized safe practiceestablish the.maxi-,

mumof voltage stress or potential difl'erence whichmay exist at. any gven distance from the h gh tension conductingline, and the. dielectr cstrength, of the insulating material of this apparatus, vat any distanceaway exposed terminal is substantially great enough to"-withstand thevoltage stress existlng at egual distances from the conduct" ing line,pre erably with a factdr'of safety. In this description the aircontainedfiri the joints betweenthe parts of the insulating casing isconsidered as an insulating medium, and these joints are madelong enoughto prevent electric discharge through them under the maximum stressoccurring at distances fromthe line conductor equal to the distances ofsuch joints from the exposed terminal of the apparatus. All of theconducti ve material in the apparatus is thus encased and protected,preventing exposure to the line, liable to cause serious damage.

The insulating casing prevents any such are or discharge from takingplace, and cooperates with the insulating holder to safeguard theoperator and the line itself when the testing instrument is used inconnectionwith a hightension electrical transmission line, The holder 12in the form of the invention here disclosed is preferably made in theform of atube. whereby it combines the characteristics of both a holderand a sound conduit: -as previously stated. The inner walls enclosing'the bore 8 of this tube in efiect con stitute the conduit elementthereof, and the material in the outer part of the tube con-v stitutesthe supportihg element or holder proper, and is of suflicient bulk,strength and rigidity to support the detector, mounted on one end ofthe'tube, when the opposite end is held by an operator. Both elementsembodied in the tube, namely, theholder element. and the conduitelement, are of good electrically insulating material hating sufcarriedby the high" tension transmission 1. lines in connection withwhichthespecific instrument is esigned to be used, when'the detector is incontact with such a line. In other words theholder isaninsulatorjrgainst high tensioncurrents. Its length is -great enou hto'enable the operator'to remain at a sa e'distanc'efrom the line whenso manipulating the holder as to place the detector in the desiredproximity to the line, or' to an insulator supporting the line." I have'"found-v that dry,wood is a'suitable material for the holder, as itcombines the necessaryv strength and rigidity .with insulating capaci- 9ty. In order to preserve these [qualities the wood is coated orimpregnated with a Water proofing material, which is. also an insulator,such as" paraflin, 011 compounds, varnishes,

and so forth Any other combination of insulating holder and insulatingsound conductor, equivalentlfor the purposesherein set forth to thespecific combination. above described, within the scope of my inventionand of the protection hereinafter claimed.

The flexible tube is provided tc continue the sound conduit to the earsof the operator and-at the same time permit free movement of the rigidholder. A vulcanized rubber .composition comprising a high percentage ofpure Para rubber is the preferred material power-carrying line. Exceptfor the danger of this nflexible v tube accidentally falling against alive conductor, the member I) alone is sufficient to provide therequired safeguard; i

The terminal ear pieces at 'do not involve any electrical equipmentexcept as they may be made of electrically insulating material for.still greater protection, but are simply adapters to bring the aircolumn from the detector to the ears and exclude extraneohs sounds. Inconstruction the may. be. of any known type, such as envelopes adaptedto. surround the external orifice of the ear '(as here shown) or asnipples adapted to enter the ehr cavity.

In using the testing device for the purposes indicated, the operatorplaces himself at a safe distance from the insulator to be tested, butat, the same time so near that when grasping the holder'at afsaf'distance from the terminal point of the detector, he may place suchterminal point in contact Witli. the parts of theinsulator Which,hedesires to test, or with the conductor attached to the insulator, ifdesired. If, then, the

terminal point iscplaced in contactivith the live conductor, or withsome part'of the in sulator' where 'a 'sufliciently high voltage stressexists, or if it is placed in a region of sufficientlyhigh voltagenearthe conductor Ior theinsulator, an electrical action takes place inthe conductors g and l of the detector, causing sound to be produced atthe the air column in the tube ;6 to'i the ears of j w l thisresistance, no signal will be given.

Thus the 'occurrence or the absence of an au-" dible signal indicatesqualitatively whether the voltage stresses existing in theregiorlexplored are high or 'lowrelatively to the volt .age conditionatthe operators standpoint;

gap,i s..longer' or shorter, and in someregular proportion to the lengthof the gap. Thus the gap is a quantitative measure of the value of thestress. By setting the gap at a length which permits an indication to bemade under a certain voltage-condition, but from which if the length ismade greater, in; indication occurs, other. -'things' .being equaL-it ispossible to ascertain by reference, .to a table of gap-settings theapproximate value of any unknown voltage stress being measured. In theuse fort'esting insulators, the presence or absence, of an mdlcat on Agreater or lessvolt-age stress isrequired I 4 to cause such mfdlcatlonsaccording as the ;When; the gap is set'for a predetermined stress whicha good insulator will stand, de-

terminesiwhether or not the particular in i sul'atorzbeing tested ,is upto-standard or is deficient. a M I In Figure 1 or the drawing the use ofthe invention is illustrated in connection with an insulator of thepintype. Here t represents the insulator as a whole and u represents thehigh tension conductor supported b it; The

point of the detector is shown as eing applied to the junction beneaththetop petticoat of the insulator, this being the location at which themost pronounced results are ob-. tained, although within the scope ofthe "vention the test may be carried out by bring-' ing the detectorincontact with or near any point of the insulator. Having regard to theprinciples hereinbefore explained," the instrumentbeing thus applied inefiect measures the voltage stress above the ground'pox tential at thepoint of application. In, such circumstances there is always adifference of potential between the different parts of the insulatorsused with high tension transmission lines, excepte -to .parts which. are

.totally defective, and the test, byshowing Whether or not the stressesat given points are within predetermined limits, determines "whether theseveral parts'ot the insulator are normal or deficient. Thus, forexample, I

if the indicator shows that the voltage stress at the point ofapplication is too high, this detective; but it the indication showsthat the operator, giving to'him an audible inthe stress is too low, theprobably correct dication of the presence of vo tage stress at the pointof examination. The foregoing statement assumes that the voltage stressis sufi'icie'nt to overcome wh-atever'resistance is ,ground isdefective,

conclusion to be drawn is that apart of the insulator between the Thesame principles and essentially the same methods of carrying out a testare used, with so-called strain type or suspension 1n= sulators as withpin type insulators. In the indicates that the pa'rt 'of-the insulatorbetelephonic receiver. This sound is carried by tween the pointtestedand the conductor is point tested and the one case the detector isplaced between the different disks of the suspension insulator,-

parts between the line and the ground, suchcondenser parts in the pintype consisting of porcelain dielectric and cement plates or films,while in. the strain or suspension type they consists of'porcelaindielectric and (ordinarily) metal plates embodied by the hardwareconnections.

The gap heretofore described is an air gap, which requires to be madeexceedingly short in the measurement of relatively low voltage. In orderto extend the range of adjustment in low voltages, I may substitute forthe air gap a vacuum gap, or a gas having a lower electrical resistancethan air. In either of these two cases, illustrated in Figure 4., Iinsert a tube w, either exhausted or containing a suitable gas undersuitable pressure, in series in the conducting circuit. A convenientplace for inserting such tube is between the terminals of the gap, asindicated in Figure 4, although other positions and other modes ofinserting such a tube are equally within the scope of my invention andclaim for protection.

In explanation of the probable causes'and actions which produce theeffects hereinbebore. described, attention is called to Figure 3 whichshows a diagram of the electrical connections which may be used in thedetector and are, in efl'ect; used in the particular embodimentillustrated inthese drawings. Here the source of potential is at theterminal point of the conductor g when such ter minal point is in theregion of voltage stress.

' The conductors leading from this point to the telephonic receiver, andincluding the adjustable gap, provide a conducting circuit of variableresistance between this source of potential and a capacity effect toground,

such capacity effect. being provided by the insulating elements of theinstrument, or the surrounding air, and the operator himself.

The receiver and condenser are in series.

multiple connection between the source of potential and the capacityefl'ect, although I the circuit between these elements may with goodeffect be a straight series effect. I 'However, the special circuitillustrated is preferred on account of the. possibility of gettingincreased efi'ects of resonance. in the receiver by properly designingthe relation between the condenser and the receiver.

An instrument or device having the same essential characteristics can beused accord ing to the same method for testing insula-' tors at thelaboratory or place of manufacture, or in any other conditions wherethey are under voltage stress,,as Well as while in actual service on theline. Also conditions cumstances than in connection with insula-.

tors may be tested and explored by means of an instrument having theessential characteristics of this invention. lnother conditions of usethan that particularly described and illustrated, other modes ofsupporting or mounting the instrument than by the man.- ual action ofthe operatoor may be employed, all within the scope of my protection.

While the form of the invention here particularly illustrated iseflicient and satisfactory, and is preferred to other possible forms forsome purposes, nevertheless it is to be understood that various"modifications both in construction, arrangementand num her of the partsthereof have'been used successfully-by me, and others may be used wlthlnthe general principles of the invention. Thus, for example, thecondenser may be otherwise arranged with relation to the telephonicreceiver, or, indeed, may be omitted entirely as aseparate'element,without destroyingthe ability of the'detector to give the" resultsdescribed. There is always sufiic-ient inductance and capacity in theconductors and telephonic receiver for oper-1 capable of giving suchindications under the conditions contemplated is the equivalent of suchreceiver. Other modifications may be made in the arrangement,construction and disposition of the various insulating and soundconducting parts of the apparatus.

I claim:

1. A device for testing the insulating qualities of insulating units ofhigh tension electrical transmission lines under voltage stress,comprising a terminal conductor adapted to be placed at points in thevicinity of such an insulating unit where voltage stress occurs, meansfor giving audible indications,- in response to the effect of suchstress, and associated holding" and sound conducting elements extendingfrom said indicating means for placing the terminal con ductor at thepoint of test and conducting said signals to an operators ear, and beingof suflicient length to extend from the operator to such an insulatingunit while the operator himself is at a safedistance away from the pointof voltage stress; and said elements having sufiicient insulating valuestress comprising a conducting element adapted to be placed in closeenough proximity to such unit to be afiected by the Volt- 7 agestressthere existing, means in connection with said element and aifected bysuch voltage stress for producing audible signals,

1 aninsulating ca'smg enclosing said indicat- 2 mg means and all of saidconducting element except the. terminal thereof, and preventinggrounding of any electrically conductive parts of the apparatus undercon- 3. An apparatus for testing the insulating qualities of insulatingunits of high tension electrical transmission lines under voltage stresscomprising a conducting element adapted to be placed in close enoughproximity to such unit-to be afi'ected by the nection with. said elementand affected by' voltage stress there existing, means in consuch voltagestress for producing an audible signal, and an insulating casingenclosing- 'said indicating'means and all of said conducting el'ementexcept the terminal thereof, said casing atany given point having suflicient dielectric strength to withstand the maximum Voltage stressnormall'y existing between the conductor of a high tension electricpower transmission line and any i point in the neighborhood of suchconductor at a distance from the conductor equal to the distance of saidgiven point from the l exposed terminal of said conducting ele- 1electrical transmission lines under voltage 'stress comprising aterminal conductor adapted to be placed at a. point in-the vicinity ofsuch an insulating unit where voltage stressoccurs, means for givin'dlcation's actuated by the e ects of such stress, an insulating casingenclosing said 1ndicating means and all of said conductor ex cept theterminal thereof, said casing having suflicient insulating value towithstand the i maximum voltage stress normally existing in any locationwhere said indlcatmg means may be placed while the terminal of saidconductor is in contact with such insulator or the lmeconductor; andassociated holding and sound conducting elements extendin from saidterminal to such a distance, an having such insulatingvalue that anoperat'or making contact Wlth the portions of said "4. An apparatus fortesting the insulating qualities of insulating units in high tensionaudible inelements more remote from said terminal is at asafe distanceawayfrom the point of voltage stress. 1

5. A detector for indicating voltage stress at and in the vi'cinityiofhigh tension electrical transmission-lines comprising anins'ulatminaladapted to be placed at a point where voltage stress exists,aninsulating holder for ing'casing, an electrical conductor enclosed 1nsaid casmg and having an exposed tersaid casing, means in said casingfor producing sound in response to electrical action resulting fromplacement of said terminal at such point, and insulating soundconductingmeans forzt ransmitting the sound so produced' to the operators ear;said-casing, holder and sound conducting means having sufficientdielectric strength to prevent short ,circuiting through any part of theapparatus when said terminal is in a region of voltage stress of. theorder of magnitude of that existing at and adjacent to a high tensionelectrical power transmission line, and said holder having'a lengthsufficient to interpose a safe distance betweehan operatorgrasping'itand the region of high potential volt agestress when said terminalisplaced at a point in such region. a

-6'. An apparatus for indicating voltage stress at and'inthe vicinity ofhigh tension electrical transmission lines comprising an insulatingcasing, an electrical conductor enclosed in said casing but having anexposed terminal adapted to be placed at a point. where voltage stressexists, indicating means within and enclosed by said casing operative toproduce sound in responseto electrical action resulting from placementofsaid terminal at said point, an insulating holder on which said casingis mounted, said holder having sufficient stiffness, to support and movethe above described electrical equipment when grasped by an operator ata point remote from thesaid electrical equipment, and; having sufiicientlength and dielectric Inn strength between said equipment "and thegrasping point to prevent electrical discharge to the operator from thesaid point of voltage stress adjacent to a high tension electrical powertran'smissionline; saidholder having also a sound conducting channelleading from the interior of said casing where said indicating means iscontained.

7. An apparatus for indicating voltage stress at and adjacent to hightension electrical transmission lines comprising an electrical conductorhaving an exposed terminal adapted to be placed at a point where voltagestress exists, indicating means in connection with said conductoroperative to prov duce sound in response to electrical action resultingfrom placement of said terminal at said point, an insulating holder onwhich said conductor; and indlcating means are mounted, said holderhaving suflicient stifi- ,ness to support and move the above describedelectrical equipment when grasped by an operator at a point-remotefromthe said electricalequipment, and having suflicient length anddielectric strength between said equip' ment and the grasping point toprevent electrical discharge from the said point of volt age stressadjacent to high tension electrical power transmission line, to theoperator; said holder having also a sound conducting channel leadingfrom the interior of said indicating means, and a flexible continuationtube of insulating material extending from the end of said channelremote from the indicator and having an orifice adapted to be placed atthe ear of an operator.

, 8; An apparatus of the character described oomprising electricaldonductors in series but mechanically separate from one another,

insulating bodies enclosing both conductors except the terminalextremity of one of them, said bodies having telescoping portionsadjustable one on the other to obtain a gap of variable length bet-weenthe adjacent ends' the magnitude of that existing in a high tensionelectrical power transmission line"; an electrical sound producingdevice in connection with the other of said conductors and operable bysuch voltage stress, an insulating cas ng enclosing said indicator andan insulating sound conductor leading from said casing,

9. An apparatus of the character "described comprising an electricalconductor having aterminal adapted to be placedat a point where highvoltagestress exists, an electrical sound producing apparatus inconnection with said conductor, an insulating casing completelysurrounding said conductor and sound producing apparatus, and aninsulating sound conducting member con- P nectedto said casing andhaving an orifice in position to receive sound waves ropagated by saiddevice; the casing having at i any point sufficient dielectric strengthto and adjacent to a high ductor terminal is subjected to voltage stressof the order of magnitude of that existing at tension electrical powertransmission line. f

10. A detector for measuring voltage stress comprising a casing ofinsulatingrnateria l, a telephonic receiver in said casing, a

conductor in connection with said receiver 7 and a second conductorenclosed within the ductor but mechanically separate therefrom and havinan exposed end,"one of said concasing in series with the first namedconduc tors being adjustably mounted relatively to the other, whereby toproduce between them a gap of variable width, and said detector beingadapted for placement with the exposed terminal of the second conductorat a point of voltage stress, whereby the electrical action occurring insaid conductor causes the receiver 'tomake'va' sound, the length of saidgapbeing a measure of the voltage stress which is great enough to crosssaid gapand eau'sesound producing action of the receiver. i j

11. In a testing apparatus for testing the insulating value ofinsulating units for high' tension electricakpower transmission linesunder voltage stress, having electrical con ductors in series butmechanically separate from one another, insulatin bodies enclos ing bothconductors excepttremity of one of them, said bodies having telescopinportions adjustable one on the other to obtain a gap ofvariable lengthbetween the adjacent eiidsof said conductors, the length of saidtelescoping portions being such as to provide air gap insulationsufficient to withstand the maximum normal voltage stress towhich it issubjected when said terminal is in a region of voltage stress of the.magnitude of that existing in such a ower line, and said insulatingbodies havng like insulating value. j y

In testimony whereof I have aifixed my signature.

FRANK o. DOBLE.

the" terminal ex

